It has been known that plastic articles can be strengthened by molding the plastic around a solid core. Many articles are so constructed. Also, tubular articles have been filled with foam plastic to provide strength with lightness. Therefore, there are many combinations of solid cores or hollow items used in combination with plastic material to provide strength and rigidity with a minimum of weight. However, most of these articles must be assembled, joined, or otherwise constructed in a conventional manner, using nuts and bolts, nails, glue, or other conventional joining means.